Something I don't get about heat treating boolits

[Don1357]

So you are not supposed to size after treatment because that will soften the boolit, but isn't that what happens the millisecond that boolit hits the lands and gets squeezed into the barrel?

[Dusty Bannister]

No, age softening is not instantaneous, but occurs over time.

[Rcmaveric]

You can size after heat treating. It takes time for hardening to occur. Lead does what is called precipitation hardening (ie the crystals grow at room temp). It is encouraged to size after treating because after a week or so its going to be harder on you and your press to size them. Sizing will bot impacted your finnal hardness.

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[Rcmaveric]

Tin alloys age soften while antimonial lead age hardens. I was reading an article and after seven years antimonial lead loss negligible harndness after heat treating

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[Don1357]

These are not what I'm talking about. I'm referring to the notion that sizing after heat treatment would work-soften the alloy rendering the process moot.

Either the alloy can get work softened and the whole thing is pointless (shoving the oversize boolit into the barrel being the ultimate work-softening there is) or work-softening is not that significant under shooting so it would stretch credulity that it could have a significant impact during resizing.

[Rcmaveric]

These are not what I'm talking about. I'm referring to the notion that sizing after heat treatment would work-soften the alloy rendering the process moot.

Either the alloy can get work softened and the whole thing is pointless (shoving the oversize boolit into the barrel being the ultimate work-softening there is) or work-softening is not that significant under shooting so it would stretch credulity that it could have a significant impact during resizing.Any work softening is insignificant.

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[winelover]

Plenty of casters, get good results from water dropping their alloy. Going this route, unless you use them as cast, you are sizing after heat treating. I don't water drop. I air cool all my alloy. Install gas checks, by running through the sizer, without lubing. Either, a RCBS LAM or a Star. After that the bullets are heat treated in a convection oven, immediately quenched in ice water. Towel dried, then ran again through a slightly oversize die, to receive their lube. So work hardening is at a minimum.

The theory of hardening being effected when bullet enters the rifleling is questionable. Surface heat treating should penetrate, deeper than the engraving.

Winelover

[JonB_in_Glencoe]

So you are not supposed to size after treatment because that will soften the boolit, but isn't that what happens the millisecond that boolit hits the lands and gets squeezed into the barrel?

This is my take on it...
What makes a heat treated boolit more accurate than a boolit of the same alloy that isn't heat treated?
The answer is boolit deformation due to pressures that are higher than the non-heat treated boolit can stand.
Pressures go down the instant the boolit starts moving.
In a high pressure load, the extra hardness is needed to get a square launch and a straight entry into to leade. Once the majority of boolit is being squeezed through the rifling, the pressure is likely low enough to not deform the alloy, other than what the barrel rifling is doing.

While I don't size heat treated boolits after treating...If I were too, I suspect the thin outer layer that is work softened isn't going to be a factor in the launch or the entry into the leade.

[blackthorn]

My opinion--: Trying to compare any possible softening effects on bullets that are heat-treated (and likely stored for days, weeks, or even years) with a bullet that is fired into a tight(er) bore, is like comparing apples to oranges. In the first instance, the bullet sits and any possible changes in BHN occurs over an extended time, whereas a fired bullet is under pressure for a nanosecond and is well on its way (if not already at its final destination) before any negative changes can occur. As I said, just my opinion.

[Don1357]

My opinion--: Trying to compare any possible softening effects on bullets that are heat-treated (and likely stored for days, weeks, or even years) with a bullet that is fired into a tight(er) bore, is like comparing apples to oranges. In the first instance, the bullet sits and any possible changes in BHN occurs over an extended time, whereas a fired bullet is under pressure for a nanosecond and is well on its way (if not already at its final destination) before any negative changes can occur. As I said, just my opinion.

Again, I'm not talking about age softening but about alleged softening that happens at sizing. If sizing by hand is enough to soften a bullet, it follows that sizing the bullet with the barrel with 30k PSI pressure ought to soften the boolit even worse.

It just sounds to me that the common wisdom of sizing a heat treated bullet would soften it may be wrong.

[gwpercle]

Heat treating is not exactly the same thing as water dropping .

Heat treating involves casting and sizing the boolits , then standing them upright in a tray . The tray is placed in an oven and baked at a prescribed temperature , just below the melting point of your alloy . After heating for a prescribed time the tray of boolits is removed from the oven and placed into a container of cool water . The tray should have handles and holes in the bottom and sides to let the water cool each one evenly...mine does . Next the pre-sized hardened boolits are lubed with no additional sizing . This is a heat treated boolit .

Water dropping is simply dropping boolits out of the mould into cool water, it does pick up some harness but not as much as a heat treated boolit will be . The water dropped will loose some hardness if sized by the cold working of the bearing surface .

Probably all this is moot...once the boolit gets going down the barrel all bets are off.

My solution is 50-50 COWW / lead , air cool , size and if speed is needed use a gas check !
Gas checks can make your life so much easier...don't be afraid of them .
Gary

[megasupermagnum]

Again, I'm not talking about age softening but about alleged softening that happens at sizing. If sizing by hand is enough to soften a bullet, it follows that sizing the bullet with the barrel with 30k PSI pressure ought to soften the boolit even worse.

It just sounds to me that the common wisdom of sizing a heat treated bullet would soften it may be wrong.

I've had the same thoughts as you, and have shot them both ways. I even measured a couple post-HT sized bullets for hardness. Zero change in the middle of the bullet. If there is any slight work softening of the outside from sizing, there is no way to prove it. That said, sizing a 30 BHN bullet is not that great, and often distorts the base because of it. With my COWW alloy I get about 25 BHN from water dropping, 30 BHN from heat treating, or 13 BHN from air cooling, all measured after about a month. Water dropped bullets significantly harden almost immediately, and I never did find a way that didn't damage too many bullets when dropping into a bucket. I only heat treat currently, and pre-size them to make life easier.

[Rcmaveric]

I have been reading some books. Check out the article on heat treating in the NRA cast bullet supplement. Heat treating and water dropping from the mold induce the same effect. The article goes into depth about this.

The supplement recommends sizing first then heat treating. Then lubing with a sizer die .001 over the bullet diameter. Sizing doesnt alter the metals BHN. It does change the grain boundaries BHN when the bullet is elongated by sizing. So i learned something today. The grain bondary is what holds the bullet together.

The lands and throat will do the same thing to a bullet. But it will resist and have its strength upon firing. Which is when the bullet needs it the most. After that pressures taper off. Transition from the case mouth, through the throat and the first inch of the barrel is the most important time of bullet.

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